Scrimmage kick play

[NCVAReferee]

K 4/10 @50.  K1 punts the ball high and short.  R33 muffs the kick at R-35.  The muff rebounds behind the LOS.  K1 picks up the ball and throws a forward pass from K-47.  The pass falls incomplete.  During the pass, K66 is 15 yards downfield.

[ncwingman]

Illegal man downfield, 5 yard penalty, replay 4th down. (4/15 at K45)

What will really bake your noodle is if K66 wasn't illegally downfield. The result of the play is 1st and 10 for K at the 50. Since R muffed the kick beyond the LOS, the team in possession of the ball at the end of the play is awarded a new series. As K legally recovered the ball behind the LOS they can advance (or throw a pass) -- the result of an incomplete pass is still K's ball at the previous spot, but now it's 1st down for K.

However, since K committed a foul during the down, the down (4th) is replayed if the penalty is accepted. Do NOT let R decline the foul thinking that the result of the play is a turnover on downs.

[VALJ]

Illegal man downfield, 5 yard penalty, replay 4th down. (4/15 at K45)

What will really bake your noodle is if K66 wasn't illegally downfield. The result of the play is 1st and 10 for K at the 50. Since R muffed the kick beyond the LOS, the team in possession of the ball at the end of the play is awarded a new series. As K legally recovered the ball behind the LOS they can advance (or throw a pass) -- the result of an incomplete pass is still K's ball at the previous spot, but now it's 1st down for K.

Don't forget to enforce the USC on the R coach.  There's no way in the world he's going to accept that the other team kicked the ball AND threw an incomplete pass on the same play and STILL gets the ball 1/10.  That conversation is going to turn ugly. 

However, since K committed a foul during the down, the down (4th) is replayed if the penalty is accepted. Do NOT let R decline the foul thinking that the result of the play is a turnover on downs.

Definitely.  Might even be worth walking the R captain over to in front of their bench and explaining the options very loudly so that the head coach can hear...